<!DOCTYPE html>
<html>
<head>
<title>Table border collapse</title>
<style>
  table {
    border-collapse: collapse;
    height: 100px;
    width: 100px;
  }
  td {
    background-color: black;
    border-radius: 50px;
  }
</style>
</head>
<body>
  <table>
    <tr>
      <td></td>
    </tr>
  </table>
</body>
</html>